Fluid pressure control



p 1935. o. c. WRIGHT FLUID PRESSURE CONTROL Filed April 1, 1955 Inventor O. C. Wright Att'y.

Patented Sept. 3, 1935 UNjlTED STT 8 Claims.

My invention relates to a fluid pressure control and particularly to a control such as may be adapted for use in applying the brakes of a street car, automobile, or other motor driven vehicle.

One object of my invention is to secure the maximum speed of response in both brake application and release. This result is obtained by the use of electrically-operated valves controlled by a contact movable under two opposing forces, one of which is varied manually, and the other by the pressure of the brake applying fluid.

Another object of my invention is tosecure automatic application of the maximuIn brake pressure, that is, what is known in the art as emergency application, in the event of the failure of the valve actuating current. The accompanying drawing illustrates my invention diagrammatically. Figure 1 shows one form of fluid pressure control mechanism as applied to the brake cylinder of a street car or similar vehicle; and Figure 2 is a fragmentary view showing a modification.

A reservoir I supplies the compressed air or other actuating fluid through a pipe 2 to a valve casing 3 which communicates through 'a. pipe 4 with the brake cylinder 5. In the valve casing are an application valve 6 and a release valve '1, the former being biased toward open position and the latter toward closed position. These valves are actuated by electromagnetic means hereinafter described. Leading from the pipe 4'is a pipe 8 supplying pressure to a tubular spring 9 of annular form acting as a pressure gauge of the type known as a Bourdon tube. The ends of the tube are connected by links IE to a contact arm I I pivoted at I2. The end of the contact arm moves between two stationary contacts I3 and I4. As the contact arm is itself grounded, it functions to ground either of the stationary contacts with which it engages. When fluid under pressure is supplied to the gauge, it tends to separate the ends connected by the links to the contact arm and thus swing the arm on its pivot toward the contact I3, while the resiliency of the tube tends to move the ends toward each other and so swing the arm toward the contact MJ Secured to the arm I I is a lever 'I 5 bearing on a spring is, the tension of which may be varied by moving a lever ii on its pivot I8. Lever I1 is movable between stops I9 and 28 by means of a handle or treadle 2 I being normally held against the stop I9 by a. spring 22 of sufiicient strength to overcome the tension of spring I6. The parts are so proportioned and adjusted that the maximum tension of spring It, when lever I! is against stop I9, is just sufficient to overcome the tension of tube 9 and hold the contact arm against contact IS.

A source of E. M. F., such as battery 23, is grounded at one terminal, the other being connected by line wire 24 to ground. Line 24 includes a solenoid 25, which, when energized, moves re lease valve i to open position, as shown. Line 24 includes a circuit breaking switch 26 biased toward open position. This switch is closed by a solenoid 2'! contained in line '28 connected at one end to line 2 and at the other to contact I3. When arm II is in contact with IS, current will be supplied to solenoid 27 holding switch 25 in closed position and so supply current to solenoid 25 to hold the release valve in open position. When arm I I moves out of contact with I3, switch 25 will open, breaking line 24 and so allowing the release valve to close. Leading from line 24 is a branch 29 passing through a solenoid 3G for closing the application valve 6. This line is grounded and includes a circuit breaking switch 3|. This switch is biased toward open position and is closed by a solenoid 32 included in a line 33 grounded at one end and connected at the other to contact I4. Current is supplied to line 33 from the battery 23 through a resistance 34 of such value as to permit the passage of suificient current to actuate solenoid 32 but to prevent undue drain on the source of E. M. F. when arm II is in contact with I3. Contact of I I with I4 30 short circuits line 33, deenergizing solenoid 32, thus opening switch 3! to break line 29 and allow the supply valve to open.-

In the operation of my device, the parts being in the position shown, to apply the brakes, lever 35 I! is depressed, lessening the tension of spring I6. As the maximum tension of this spring is just sufiioient to overcome the tension of tube 9, this will permit the tube to move arm II out of contact with I3. This breaks circuit 28, deenergizing solenoid 21 opening line 24, thus permitting the release valve to close. Further depression of lever I1, with consequent decrease in tension of spring I6, permits tube 9 to move arm II into contact with I i, short-circuiting line 33 to deenergize solenoid 32, thus opening switch 3| to deenergize solenoid 39 and permit the application valve to open. This will supply fluid under pressure to the brake cylinder 5, and at the same time through pipe 8 to the gauge tube 9. As soon as suificient pressure is admitted to the tube to overcome its tension, arm II will be moved out of contact with I4, closing the application valve 6, thus bringing the braking system to what is known as lap position. The pressure at which this will occur will depend upon the amount of depression of lever I1 and the resultant tension of spring l6 and may be varied from minimum to maximum braking force. To release the braking pressure, lever II is allowed to rise under pressure of spring 22. This increases the tension of spring l6, moving arm I I into contact with IS and so opening the release valve. In case lever ll is allowed to rise into contact with stop IS, the valve will remain open until the entire content of the brake cylinder is discharged. If the lever is allowed to rise less than this distance, the tube 9 will overcome the combined pressure of the fluid in it and the lessened tension of the spring 16 before the cylinder is reduced to atmospheric pressure and will move arm H out of contact with l3 to bring the system again into lap position, in this case by the closing of the discharge valve rather than by the closing of the application valve, as in the brake applying operation. If at any time the current supply fails, the application valve will open or remain open and the release valve will close or remain closed, thus insuring emergency application of the brakes when this occurs.

In Figure 2, I have shown a modification, particularly adapted to use in connection with an automotive braking system, in which, when the control is completely released, the brake will not be released but will be applied with a pressure less than the emergency or full pressure application. In the modification a link 35 is provided, having a pin and slot connection with the lever IT. This link is pivoted to a lever 36 fulcrumed at 31 and actuated by pressure at its end 38. In this construction the part 2| will preferably be in the form of a toe pedal and the part 38 in the form of a heel plate located adjacent thereto so that both may be operated by'the same foot of the motorman. A spring 39 normally holds lever 36 against a stop 40. The spring 39 must be of sufficient strength to overcome the tension of spring 22.

In this form of my device, when the lever 36 is depressed by pressure of the motormans heel on plate 38, link 35 is raised to such a position that the pin and slot connection will not interfere with the movement of the lever l'l between stops l9 and 2!], and the operation of the system will be as above described. When, however, pressure on the heel plate is released, spring 39 will move lever 36 against stop 40, lowering link 35 to such position that the pin will contact with the end of the slot before lever "has been raised into contact with stop l9. This will result, when pressure on toe pedal 2| is released, in bringing the valves to lap position with a predetermined pressure, less than full pressure, in the cylinder 5.

Having fully described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the flow of fluid from said source to said chamber, electromagnetic means including a pair of contacts governing the operation of said valves, a member movable between said contacts, said member cooperating with one of said contacts to control the movement of one of said valves .and with the other contact to control the movement of the other valve, means biasing said member toward one of said contacts, the action of said biasing means being modified by the pressure in said chamber, yielding means biasing said member toward the other contact, and manually-operated means for varying the tension of said yielding means. 7

2. In a device of the class described, the com bination with a source of fluid supply, of a pressure chamber, application and release valves controlling the flow of fluid from said source to said chamber, electromagnetic means including a pair of contacts governing the operation of said valves, a member movable between said contacts, said member cooperating with one of said contacts to control the movement of one of said valves and with the other contact to control the movement of the other valve, means biasing said member toward one of said contacts, the action of said biasing means being opposed by the pressure in said chamber, yielding means biasing said member toward the other contact, and manuallyoperated means for varying the tension of said yielding means.

3. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the flow of fluid from said source to said chamber, electromagnetic means including a pair of contacts governing the operation of saidvalves, a member movable between said contacts, said member cooperating with one of said contacts to control the movement of one of said valves and with the other contact tocontrol the movement of the other valve, a tubular gauge biasing said member toward one of said contacts, said gauge being connected with the pressure chamber, and spring means biasing said member toward the other contact, said spring means being manually I variable.

4. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the flow of fluid from said source to said chamber, electromagnetic means including a pair of contacts governing the operation of said valves, a member movable between said contacts, said member cooperating with one of said contacts to control the movement of one of said valves and with the other contact to control the movement of the other valve, means biasing said member toward one of said contacts, the action of said biasing means being modified by the pressure in said chamber, manually variable means biasing said member toward the other contact, and automatically operating means for limiting the action V of said manually variable means to bring the valves to a predetermined lap position at an intermediate brake pressure.

5. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the flow of fluid from said source to said chamber, a pair of contacts, a member movable between said contacts, two opposing forces acting on said member, one of said forces being varied by the pressure in the chamber and the other being variable by manual means, a main electric circuit including magnetic means for operating one of said valves, a branch circuit including magnetic means for operating the other valve, and a pair of relay circuits-for opening and closing said main and branch circuits through the engagement of said member with said con-:

tacts.

6. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the flow of fluid from said source to said chamber, a pair of contacts, a member movable between said contacts, two opposing forces acting on said member, one of said forces being varied by the pressure in the chamber and the other being variable by manual means, a main electric circuit including magnetic means for operating one of said valves, a branch circuit including magnetic means for operating the other valve, a pair of relay circuits for opening and closing said main and branch circuits through the engagement of said member with said contacts, and a resistance connecting one of said relay circuits to the main circuit.

7. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the supply fluid from said source to said chamber, electrical means for operating said valves including a pair of contacts, a member movable between said contacts, a tubular gauge connected to said member, the elasticity of said gauge biasing said member toward one of said contacts, resilient means for moving said member toward the other contact, said resilient means being sufficient to overcome the elastic biasing force of the tube, said tube being supplied with chamber pressure operating against its inherent elasticity, and manually-operated means for reducing the tension of said resilient means.

8. In a device of the class described, the combination with a source of fluid supply, of a pressure chamber, application and release valves controlling the supply of fluid from said source to said chamber, a main circuit including a source of E. M. F. for actuating one of said valves, a branch circuit for actuating the other valve, 2. pair of contacts, a relay circuit connected to one of said contacts for opening and closing the main circuit, a second relay circuit connected to the other contact for opening and closing the branch circuit, a member movable between the contacts, and two opposing forces acting an said member, one of said forces being varied by the pressure in the chamber and the other being varied by manual means.

0. C. WRIGHT. 

